*Review* **Quo Vadis: AlCr-Based Coatings in Industrial Applications**

**Joerg Vetter 1,\*, Anders O. Eriksson 2, Andreas Reiter 2, Volker Derflinger <sup>2</sup> and Wolfgang Kalss <sup>2</sup>**

<sup>1</sup> Oerlikon Balzers Coating Germany GmbH, Am Boettcherberg 30–38, 51427 Bergisch Gladbach, Germany

<sup>2</sup> Oerlikon Balzers, Oerlikon Surface Solutions AG, Iramali 18, LI-9496 Balzers, Liechtenstein; anders.o.eriksson@oerlikon.com (A.O.E.); andreas.reiter@oerlikon.com (A.R.); Volker.Derflinger@oerlikon.com (V.D.); wolfgang.kalss@oerlikon.com (W.K.)

**\*** Correspondence: joerg.vetter@oerlikon.com

**Abstract:** AlCr-based hard nitride coatings with different chemical compositions and architectures have been successfully developed and applied over the last few decades. Coating properties are mainly influenced by deposition conditions and the Al/Cr content. The fcc structure is dominant for an Al-content up to Al0.7Cr0.3N and is preferred for most cutting applications. Different (AlCr*X*)N alloying concepts, including *X* = Si, W, B, V, have been investigated in order to enhance oxidation resistance and wear behaviour and to provide tribological properties. AlCr-based oxynitrides and even pure oxides (Al1−*x*Cr*x*)2O3 with different crystalline structures have been explored. Multiand nanolayered coatings within the AlCr materials system, as well as in combination with (TiSi)N, for example, have also been implemented industrially. The dominant deposition technology is the vacuum arc process. Recently, advanced high-power impulse magnetron sputtering (HiPIMS) processes have also been successfully applied on an industrial scale. This paper describes basic coating properties and briefly addresses the main aspects of the coating processes as well as selected industrial applications.

**Keywords:** AlCr-based; CrAl-based; (AlCr*X*)N; (Al1−*x*Cr*x*)2O3; arc; HiPIMS; nanolayers; nanocomposite; structure; properties
